- Welliver appeared in the film Twisted with Mark Pellegrino, who would later play Welliver's rival Jacob on Lost. Both actors also played antagonists on Prison Break in four subsequent episodes (Pellegrino appeared Season 4 episodes 13 and 14, and Welliver in episodes 15 and 16). He played "War", one of the Four Horsemen, in the series Supernatural, alongside Mark Pellegrino, who played the fallen angel Lucifer.
- Welliver is the fifth actor from the HBO series Deadwood to appear on Lost following Kim Dickens (Cassidy Phillips), Paula Malcolmson (Colleen Pickett), Robin Weigert (Rachel Carlson), and William Sanderson (Oldham) respectively. John Hawkes (Lennon), also from Deadwood, has since appeared beginning in Season 6.
- Welliver is the ninth actor to appear in Lost and in the Fox series Prison Break, following Mark Pellegrino (Jacob), Jodi Lyn O'Keefe (Ava), Michelle Forbes (Karen Decker), Kevin Dunn (Gordy), Diana Scarwid (Isabel), Anthony Azizi (Omar), William Mapother (Ethan Rom), and Dylan Minnette (David Shephard).
- The second actor from Carlton Cuse's own Nash Bridges, following Cheech Marin (David Reyes).
- Has a recurrent role as State Attorney Glenn Childs on the legal drama television series The Good Wife, which premiered on CBS on September 22, 2009.
- Portrayed Colonel Hoffman in the season one finale of Jericho.
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